1. Get the biggest tank you have the time, space, and money to maintain properly. Rapid fluctuations in water parameters are absolutely deadly to aquarium inhabitants no matter how hardy they are and the bigger the tank the more water volume you have and the more water volume you have the more dilution you have so that changes happen more slowly meaning less fluctuation and giving you more time to catch anything out of whack and correct it early on (how's THAT for a run on sentence bad enough to make an English teacher cringe????
) Just keep in mind too that the bigger the tank the more expensive everything is going to end up.
2. There's loads of fish that will do well with a clownfish! I'd suggest taking a look around, on this site, others, fish stores, etc. and make a list of what you like. From there you can learn more about each creature and figure out what can fit with what. You can also post a list here and people are always full of opinions that you may find helpful!
3. No matter what it's best to start with fish only and then as you become more experienced at keeping the tank and the tank is matured (usually about 6 months to a year) you can start adding reef creatures if you decide to do a reef tank. So one option is to set you tank up as a fish only with liverock (FOWLR) tank and upgrade down the road since you'll almost certainly have to upgrade filtration and lighting for many of the corals and such. The other way to go is to research the requirements of reef creatures you know you'll want to add down the road and simply buy the filtration and lighting that they will require right off. It all just depends on your financial situation. Do you have enough money to plunk down all at once for the best stuff or do you need to pay a little less at first then save up for upgraded bits and pieces?
4. Keep in mind when stocking your tank with fish that if you eventually want to do a reef tank you'll need to go more light on fish. Opinions vary a lot but for a fish only tank I usually count on roughly 1" of fish for 3 gallons or so, for a reef tank more like 1" of fish per 5 gallons or better.
5. A list of things you NEED is tough but a list of good choices might be:
- tank of course
- enough RO/DI water to fill it the first time then enough later for top offs and water changes (tap water dechlorinated with drops is just an algae headache waiting to happen so count on buying RO/DI or purchasing your own RO/DI unit)
- salt mix
- substrate (sand seems most preferred)
- submersible heater (one with enough watts for your size tank will do but, IMO, it's better to split it into two heaters so if one goes down the other is backup)
- lid, glass or hood (although some people prefer an open top)
- filtration: Oh it gets really tricky here! There's such a huge load of choices on filtration so you'll have to learn about them and choose what seems best for yourself. I think some good options are liverock, cannister, protein skimmer, and sumps in different combinations depending on livestock, tank size, etc. Most people seem to feel that liverock and a protein skimmer are must haves then add an additional filter. Sumps are great choices because it increases your water volume plus you can house your heaters and such in there to hide them. Other choices are undergravel (not a favorite as detrious gets trapped beneath the plate but still in use by some), hang on the back power filter and quite a few others. I also think that refugiums are well worth looking into.
- lighting: fish aren't picky about lights so the regular old flourescents do fine for them but many reef creatures need more intense, and more expensive, lighting. Most people seem to prefer power compacts and/or metal halides.
- thermometer
- hydrometer (although refractometers are more accurate so are preferred)
- a full test kit (Salifert is said to be the most accurate)
